Fabrication of microelectronics devices makes effective use of patterned microelectronics conductor layers employed as interconnections for signal and power propagation by separating such conductor layers by means of blanket and/or patterned dielectric layers. Advances in speed and performance requirements, along with decreases in dimensions have made the requirements placed upon such dielectric layers more stringent with respect to lowering the “relative dielectric constants” of the dielectric layers (i.e., the dielectric constants relative to vacuum). The “relative dielectric constant” of a dielectric layer is hereinafter referred to for brevity as the “dielectric constant” of the dielectric layer. Dielectric layers having a lower dielectric constant are typically disposed between and around patterned microelectronics conductor layers during the fabrication process. Such dielectric layers reduce parasitic capacitance and cross-talk.
Due to the availability of many kinds of polymers with such desirable properties as high elongation, low dielectric constant, low surface energy or critical surface tension, polymers are used with increasing frequency in VLSI processes. Such alternative low dielectric-constant layers may be formed over microelectronics substrates by, among others, spin coating deposition of intrinsically low dielectric constant materials such as organic polymer spin-on-polymer (SOP). Dielectric layers can exhibit somewhat lower dielectric constants which range from about 2-3. Organic polymers SOP materials include polyimide organic polymer SOP, poly (arylene ether) organic polymer SOP and fluorinated poly (arylene ether) organic polymer SOP. The above-mentioned dielectric materials require thermal curing to form stable dielectric layers from the spin-on-polymer (SOP) dielectric materials. Thermal curing can adversely affect the dielectric constant of the polymer.
The processing steps implemented during the VLSI fabrication can also deplete or degrade some of the very properties for which the polymer is used. For example, soft etching, RF soft etching or ion milling etching are typically used as pretreatment steps. The pretreatment steps can damage the dielectric properties as they can cause the release of surface organic atoms such as carbon, oxygen and nitrogen. For example, polyimide is a common dielectric insulation whose imide group readily decomposes by ion etching. By way of another example, ion milling is also destructive of the surface organic atoms of the polyimide material.
Conventional methods of recovering the properties of dielectric material include ozone treatment, nitrogen sputtering, vaporized fluid treatment, gas diffusion or wet treatment. However, the conventional methods are expensive, inefficient and inaccurate. Hence, there is a need for method and apparatus for polymer dielectric surface recovery.